Not much is yet known about the film, other than that its screenplay is by Gregg Hurwitz, who was involved in the most recent V series and has Orphan X at the option stage with Bradley Cooper (American Sniper). He is a published author who has also written comics for Marvel (Wolverine) and DC (Batman), but The Book Of Henry is an original script. Which unfortunately means there is no source to plunder for details and no clue as to Watts' role.
It has clearly been around for some time, however, since Trevorrow says, "Book Of Henry is a remarkable piece of screenwriting that has stuck with me for years. I feel very fortunate to be able to tell this story. It is a true original."
Shooting is pencilled in for later this month in New York.